Polyurethane compositions and their use as luting agents

ABSTRACT

Polyurethane and poly(urea)urethane compositions as specified below are utilized as luting agents, for filling cavities or spaces in human or other animal bones, and are introduced in liquid form and formed in situ to create a polyurethane or poly(urea)urethane elastomer which is relatively compatible with the surrounding tissue, has good adhesive properties, low friability, and good tear and tensile strength. The invention includes the polyurethane and poly(urea)urethane compositions disclosed and their uses in the performance of surgery in human beings and other animals. The polyurethane and poly-(urea)urethane compositions are produced by the reaction of an &#34;A&#34; component prepolymer which is the reaction product of a diiosocyanate with a diol or polyol, and a two element &#34;B&#34; component, which may be any of the polyols used in producing the &#34;A&#34; component prepolymer or a relatively short chain diol or triol or a diamine (in the case of a poly(urea)urethane) or combinations thereof. One element of the &#34;B&#34; component is relatively highly reactive and reacts with a majority of the &#34;A&#34; component. The other element of the &#34;B&#34; component is less reactive and acts as a bulking agent to facilitate mixing of the two components.

This application is a division of application Ser. No. 419,999, filed09/20/82 now U.S. Pat. No. 4,477,604.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to the field of surgery for human beings and otheranimals in which elastomeric materials are utilized as adhesives and asfillers to occupy spaces produced or permitted during surgery,particulary where bone replacement prosthenses are being inserted in ahuman being or other animal.

2. Description of the Prior Art

Artificial bones, particularly joints, have been used for many years asreplacement parts for human beings and other animals. For example, apatient with degenerative arthritis at an advanced state may not be ableto use a degenerated joint, so that it is often necessary to replace adegenerated joint with an artificial joint. Some of the common jointswhich are surgicially replaced for these purposes are knees, shoulders,hips, fingers, toes and elbows. Each type of joint requires a differenttype of joint replacement member. However, all types of joint prosthesesshare some common characteristics. The material of the prosthesis isusually metal, although ceramics or other materials may be used. Forexample, titanium and various types of chromium steel alloys arecommonly used for prostheses. The prostheses may be solid, or they maybe fenestrated (formed with windows) to allow the regenerative bonetissue to form through the windows in the prosthesis, to provide addedstability and strength to the bond between the bone and the prosthesis,and to allow the luting agent to extend through the window to provide amore secure affixation in place of the prosthesis.

A prothesis, as inserted for use, includes a narrow, elongated shankwhich projects into a generally similarly shaped, excavated cavity whichthe surgeon creates in the bone into which it is to be anchored. Thearea which is excavated to provide the space for the prosthesis shank iscalled the medullary cavity. The size of the medullary cavity is notnecessarily proportionate to the size of the shank and it may besubstantially larger. The reason for this is that the shanks come inlimited numbers of sizes, and when the surgery is performed, all of thesoft cancellous tissue in the bone proximate the shank must be excavatedin the area of the shank, in order to provide the most secure bondbetween the bone and the prosthesis.

The luting agent acts as a filler, to fill the space between thecortical or reamed section of the bone and the shank of the prosthesis.This function is obviously critical for several reasons. First of all,the material used as a luting agent must be relatively liquid oramorphous in its initial state, so that it can easily be inserted in andfill completely the medullary cavity which has been formed. It mustalso, when cured, conform closely and snugly to the shape of the shankof the prothesis. The luting agent must also provide good adhesiveproperties to the prosthesis and to the human or other animal bone inquestion. The luting agent, during the polymerization reaction in whichit solidifies and hardens, must not produce an excessively highexotherm, because the exotherm could do enormous heat damage to theadjacent tissue. The luting agent should desirably have isotropicelastic properties which are similar to the elastic properties of thecontiguous bone, so that shock absorption and therefore stress in thearea, when the prothesis is in use (as, for example, when a person witha knee prosthesis is running) is substantially uniformly distributedthrough the bone and through the hardened luting agent, a conditionwhich is necessary to maintain maximum bone strength. Lastly, the lutingagent should not be friable, because particles which break away from aluting agent are foreign bodies within the joint, and can cause severeabrasive tissue damage.

Many polymeric materials have been attempted for use as luting agents,some with reasonable success. However, none of the luting agents of theprior art is capable of achieving satisfactorily all of the foregoingdesiderata. Each has numerous shortcomings.

Polymethylmethacrylate is the most commonly used luting agent. Itslimitations are: it is exothermic in use, producing temperatures ofapproximately 100° C. which can cause tissue trauma; it is brittle and,under the stress of use, can fragmentize and these fragments canaccelerate the wear of the adjacent components of the prosthesis andcause tissue damage; it shrinks substantially during polymerization,reducing the intimate contact surface area between the luting agent andthe bone and creating stresses within the polymer itself which increasethe likelihood that the polymer will disintegrate, break down andfragmentize; and it may cause systemic hypotension during insertion.

In joint replacement surgery, there is a failure rate of almost onehundred percent of all joint replacements within five years after theyhave been inserted. This failure rate is caused by the loosening of theprosthesis as a result of the loosening of the luting agent, due toshrinkage, loss of physical properties and physical disintegration.Also, polymethylmethacrylate is not an elastomeric material, so thatwith the normal stresses to which joints are subject during extensiveuse, the polymethylmethacrylate cannot adapt, causing it to fracture andbreak apart.

There are a couple of other materials which have been utilized as lutingagents to a limited extent and without particular success. One of theseis a material called "Ostamer," which is essentially a rigidpolyurethane foam, formed by the reaction of toluenediisocyanate andwater, and which has been used to repair bone fractures. In its use,several substantial parallel grooves are sawed into the broken bone inthe direction of the elongated axis of the bone and extending beyond thebroken areas of the bone. Metal rods are inserted in these grooves andheld in place by metal bands proximate the ends of these rods. TheOstamer is then inserted to fill the sawed apertures in the bone and tohold the metal rods in place, forming a rigid polyurethane foam to holdthe fractured ends together. This use of Ostamer was not acceptable forseveral reasons, including the very high exotherm produced duringformation of the rigid polyurethane foam, which caused extensive tissuedamage. Also, the raw materials used in creating the Ostamer are toxicand the polymer, when formed, is not biostable. Therefore, thisprocedure is no longer in use.

Polyester has also been attempted for use as a luting agent, withoutsatisfactory success, because of its high exotherm, its high shrinkage,its extreme brittleness, and its chemical instability at bodytemperatures.

Reference is made to U.S. Pat. No. 4,267,299, which discloses 100% solidpolyurethanes and poly(urea)urethanes formed by spray application.

SUMMARY OF THE INVENTION

The invention comprises the use of certain polyurethane-forming andpoly(urea)urethane-forming materials, to produce, by chemical reactionin situ and with a relatively low exotherm, a "100% solid" elastomerwith isoelastic behavior whereby stresses in the elastomer aresubstantially uniformaly distributed throughout the elastomer;compatibility, whereby the elastic properties of the elastomer can bevaried to closely match the elastic properties of the adjacent bone; lowfriability, whereby the elastomer after long periods in place will notsubstantially disintegrate and cause inflammation, tissue reaction orabrasion of the adjacent prosthesis when the prosthesis is a polymericmaterial such as polyethylene; lack of shrinkage in its formation; andability to be poured readily into the medullary cavity and react rapidly(a brief "gel time") to retain physical integrity to support theprosthesis shank firmly in position within seconds after the elastomer'scomponents are mixed, to prevent displacement of the shank fromposition. These desirable features are obtained by the use of certaincomponents which form 100% solid polyurethane and poly(urea)urethaneelastomers, which may also be formed as copolymers with otherelastomeric materials, such as polydimethylsiloxane and acrylics.

As used herein, a "100% solid" polyurethane or poly(urea)urethane is onewhich, after its formation is complete, is substantially completelysolid (as contrasted to a liquid or a viscous, flowable material).

The polyurethane or poly(urea)urethane must be formed from certainspecific types of reactants, in order to assure that the reactionproduct is formed with a tissue-tolerable exotherm and with thedesirable physical properties. The "A" component prepolymer which isused to form the elastomer is the reaction product of one or morediisocyanates with one or more diols or polyols.

The "B" component may include any of the polyols utilized in preparingthe "A" component prepolymer and/or a diamine as curing agent and anysuitable short chain diol or triol as reactive fillers to form a 100%solid polyurethane or poly(urea)urethane with the desirable chemical andphysical properties of this invention.

It is desirable to use the same polyol in the curing agent of the "B"component as is used in forming the "A" component because there is lessrandomness in the resulting elastomer when this criterion is followed,thus resulting in more uniform physical properties throughout theelastomer.

One purpose of the selection of the particular reactants of the "A"component and the "B" component is to produce a polyurethane or apoly(urea)urethane which is formed from components which are liquid atroom temperature, without the use of a solvent, since solvents are veryharmful to animal tissue. The polyol is utilized as a "filler" orbulking agent to provide the requisite volume ratio between the "A" and"B" component and will participate to a limited extent in thepolymerization reaction to provide good, uniform physical propertiesthroughout the elastomer. The volume ratio of "A" to "B" component usedis important in the practice of this invention, to permit easy handlingand intimate mixing of the two components and a 1:1 ratio is mostdesirable.

The curing agent of the "B" component is the principal reactive agentwith the "A" component for the formation of the elastomer, and willfunction as a crosslinking agent or chain extender or both for the "A"component and will substantially completely react with the NCO-groups inthe "A" component within about two to five minutes after the "A" and "B"components are mixed. Thus the curing agent is said to be "highlyreactive."

The "filler" is also reactive with the NCO-groups of the "A" component,but is substantially less reactive. Thus a relatively large quantity offiller may be used with a small quantity of highly reactive curing agentto provide the required volume of "B" component to mix radily with the"A" component.

It will be appreciated that a large number of combination ofisocyanates, diols, polyols and other curing agents come within theparameters of this invention. Not all combinations of disclosedcomponents will produce the desired results and will combine the desiredchemical and physical properties. Such considerations as pharmacologicalacceptability, working time, "gel time," cure time, exotherm,isoelasticity and load bearing criteria will all be taken into accountin selecting the proper combination of components for a particularapplication or group of applications. These considerations are allwithin the purview of a skilled polyurethane chemist.

As used herein, the "gel time" is the time which elapses after an "A"component and "B" component are mixed until the resulting elastomer hascured sufficiently that it has a consistency resembling warm tablebutter.

OBJECTS OF THE INVENTION

It is therefore an object of this invention to provide novelpolyurethane and poly(urea)urethane luting agents, and processes fortheir use, for use in filling bones in humans and other animals whichhave the advantages of:

(1) Being pharmacologically acceptable;

(2) Being easily poured in liquid form at room temperature;

(3) Readily forming a "gel" to provide substantial physical support to aprosthesis shortly after its insertion and having a gel time preferablyof about five to ten minutes;

(4) Reacting to create a relatively low exotherm, not to exceedapproximately 150° F., to avoid or minimize damage to tissue.

(5) Permitting variable compositions of elastomer to be used to matchthe elastomeric properties of the elastomer with those of the adjacentbone tissue, to avoid damage to that bone tissue in use and to providean isoelastic interface between the bone and the elastomeric lutingagent;

(6) Possessing good physical properties of shear strength, elasticityand tensile strength;

(7) Not shrinking significantly with the passage of time; and

(8) Being relatively unfriable, and not disintegrating significantlywith use.

Another object of this invention is to provide a process for theaffixation in situ in a human being or other animal of a prostheticdevice comprising the utilization of a polyurethane orpoly(urea)urethane elastomer possessing the properties described above.

DETAILED DESCRIPTION OF THE INVENTION

The invention relates to certain compositions of polyurethane andpoly(urea)urethane elastomers and copolymers of such elastomers withother polymers, which are useful as luting agents for human beings andother animals, and the process of use of such elastomers as lutingagents.

As used herein, the term "luting agent" means a composition which isutilized to fill space within or between elements of human or otheranimal bone or other tissue. This may be necessary, for example, when aprosthesis is being inserted in the medullary cavity of a bone, and maybe necessary as an adhesive to fasten pieces of bone which may befractured, without the use of a prosthetic device.

The polyurethane and poly(urea)urethanes of this invention are formed bythe reaction of an "A" component, which is the prepolymer, and a "B"component, which incorporates the relatively highly reactive curingagent and a "filler." The "A" and "B" components react when mixed toform in situ the elastomeric luting agents of this invention. Thischemical reaction is exothermic, giving off heat, and must be regulatedto prevent too much heat from being given off in the elastomerformingreaction.

In the practice of the invention it is important to select theparticular "A" component prepolymer and the particular ingredients ofthe "B" component curing agent and filler so that the elastomer whichthey produce possesses the physical properties and other characteristicswhich are desired for the particular application of the invention. Thismeans that, for different applications, different prepolymers curingagents and fillers may desirably be used, and the selection of thosecomponents to achieve the desired properties is within the purview ofthe skilled polyurethane chemist, in view of the disclosure containedherein. The 100% solid compositions of this invention are formed by thereaction of an "A" component prepolymer and the "B" component curingagent and filler, all of which are selected to be pharmaceuticallyacceptable, such that:

(1) Each components is liquid and both components are relatively easilyand completely pourable and miscible at room temperature, so that theywill readily completely fill a medullary cavity.

(2) The components, when mixed, have a relatively short gel time, in therange from about thirty seconds to about twenty minutes, and preferablyabout five to ten minutes, so that within a relatively short period oftime after they are mixed as a liquid, they react and form a semi-solidgel, which possesses physical properties which are intermediate theproperties of the initial liquid mixture and the ultimate elastomer,thereby providing significant structural support to help stabilize theprosthetic device and minimize the likelihood of its displacement whilecure of the elastomer is continuing, but after it is desirable from apatient standpoint to close the surgical incision. It is important toestablish a gel time which is appropriate for the particular purpose forwhich a specific composition of the invention is being used. The geltime may not be too short or the elastomer will be hardened before theprosthesis is inserted and properly positioned in the medullary cavity.The gel time may not be too long or it will delay the closing of thesurgical incision, which is medically undesirable. The preferable geltime is in the range from about five to about ten minutes.

(3) The components, in reacting, produce a relatively low exotherm inreacting, not to exceed approximately 150° F., and preferably not toexceed approximately 120° F.

(4) The components are miscible in a ratio of part "A" to part "B" whichmakes mixing easy to do and does not require precision mixing in orderto achieve the desired reaction product. The preferable ratio of "A"component to "B" component is 1:1.

(5) The resulting elastomer has good physical properties of tensile,tear and shear strength.

(6) The resulting elastomer is isoelastic, so that it has substantiallyuniform physical properties in all directions.

(7) The resulting elastomer will not disintegrate or shrink readily withtime.

It is important to note that the components disclosed herein willproduce elastomers which, in some instances, will have some but not allof the desired attributes and will have them in varying degrees. Thecombination of qualities desired will vary from application toapplication. For example, if a luting agent for a knee joint is desired,physical properties, isoelasticity and slow disintegration are importantproperties. On the other hand, if a luting agent is desired for a fingeror toe joint, good adhesion to the bone is important, and physicalproperties are less important since the joint withstands much smallerforces.

The "A" components of this invention are the reaction products of one ormore diisocyanates with one or more diols or polyols. The diisocyanatecan be, but is not limited to, tolyene diisocyanate, methylene bisdiphenyldiisocyanate, 5,5' dimethyl methylene bis diphenyldiisocyanate,bitolylene diisocyanate, naphthalene diisocyanate, DDI diisocyanate,dianisidine diisocyanate, toluidine diisocyanate, xylylene diisocyanate,hexamethylene diisocyanate, paraphenylene diisocyanate or mixtures ofthe above.

The diol or polyol can be polytetramethylene ether glycols of molecularweights from about 500 to about 3000; polyoxypropylene glycols ofmolecular weights from 200 to about 6000; tetraethylene-glycol polyesterglycols of molecular weight from about 400 to about 3000, such as thosemade from a dicarboxylic acid such as adipic, azelaic, sebacio, suberic,pimelic, glutaric, succinic, maleic, phthalic, isophthalic andterephthalic acids and a glycol such as ethylene glycol, propyleneglycol, diethylene glycol or dipropylene glycol or mixtures of theseacids and glycols; or polylactone glycol of molecular weight from about500 to about 3000, such as polycaprolactone; but is not limited to theseacids or glycols; polybutadienes having molecular weights in the rangefrom about 400 to about 3,000; polyoxpropylene oxyethylene glycols ofmolecular weight from about 300 to about 5000; polycarbonate diols orglycols having molecular weights in the range from about 500 to about3,000; and polyisobutylene glycols having molecular weights in the rangefrom about 1,000 to about 10,000.

In forming the "A" component, the diisocyanate is desirably reacted in amolar ratio of from about 1.5 to about 12 moles per mole of polyol,which will result in an excess isocyanate content of from about 2.5% toabout 25% by weight.

The "B" component is made up of one or more relatively highly reactivecuring agents which are the primary reactant with the "A" component toform the desired elastomer. Slightly less than all of the relativelyhighly reactive curing agent needed to completely react with the "B"component is used, in order to allow the less reactive "filler" toparticipate in the urethane-forming reaction and be an integral part ofthe ultimate elastomer molecule. This is important because a relativelysmall volume of relatively highly reactive curing agent is needed toreact completely with the "A" component. This volume is typically about6-25% of the "A" component volume, so that a volumetric mixing ratio ofbetween 20 to 1 and 4 to 1 would normally be needed for a completereaction. It is difficult to get intimate mixing of "A" and "B"components when the volume differences (and potential viscositydifferences) are so great.

The ideal volume ratio for easy and intimate static mixing of "A" and"B" components is 1:1. For this reason, the "B" component is made up ofone or more relatively highly reactive curing agent in low volume plus amuch larger quantity of a relatively less reactive filler, in suchquantities that equal volumes of "A" component and "B" component willreact to form an 100% solid elastomer in which both the curing agent andfiller are chemically incorporated.

Since the curing agent reacts with most of the "A" component, it is theselection of curing agent and the quantity of curing agent whichdetermine the gel time.

The "B" component may include as the curing agent any of the polyolsmentioned above in preparing the "A" component adduct (prepolymer) orother polyol or a diamine or a combination thereof. The diamine can be,but is not limited to polyoxypropylene diamine, methylene, dianiline,methylenebis dipropylaniline, diethylated toluene diamine, toluenediamine, trimethylene bis para amino benzoate, bis (amino phenyl thio)ethane, menthane diamine and cyclohexane diamine, or mixtures of theabove diamines.

The short chain diols or triols which are used as less reactive"fillers" can be, but are not limited to butane diol, ethylene glycol,diethylene glycol, triethylene glycol, tetraethylene glycol,thiodiglycol phenyldiethanolamine, phenyl diisopropanol amine,cyclohexanedimethanol, beta hydroxyethyl ether of hydroquinone orresorcinol, trimethylolpropane, trimethylolethane, glycerol and mixturesof the above diols and triols. Compounds having both amine and hydroxylfunction can also be used, such as but not limited to polyglycol amine"H-163," which is sold by Union Carbide.

For purposes of this invention the preferred art for the "B" componentis to use as the relatively highly reactive curing agent one or more ofthe polyols used in the preparation of the "A" component and a diaminewith a less reactive filler which is one or more short chain diols ortriols. The ratio of curing agent to filler can be varied to regulatethe mixing ratio of "A" to "B" component, working life, gel time andcure time as well as exotherm and load bearing capability, and will alsovary with the type of diisocyanate and isocyanate content of the chosen"A" component.

It is, of course, essential that all components of the polyurethane andpoly(urea)urethane elastomers be pharmaceutically acceptable and ofmedical grade, so that they may properly be used in the practice of thisinvention. In the practice of this invention a given quantity of "A"component is initially mixed with a given quantity of the "B" componentto react and form the desired elastomer. In order to make intimatemixing of the "A" and "B" components easy to do, it is preferred thatthe "B" component is composed of the relatively highly reactive curingagent and less reactive filler in amounts such that equal parts of "A"component and "B" component can be mixed to form the desired elastomer.Other mix ratios can be utilized and various mechanical mixers can alsobe used to insure accurate and complete mixing of the "A" and "B"components. However, it is preferred to use a caulking gun as a mixerand applicator in which two sealed single use tubes of "A" component and"B" component are static mixed without mechanical agitation. Aconventional two-component caulking gun, made of sterilizable materials,such as stainless steel, for surgical use would be suitable and wouldhave a variety of sizes and shapes of nozzles to adapt to the differentsizes, shapes and locations of places for delivery of the elastomers ofthis invention.

It is also possible to mix the "A" and "B" components by hand in asterile vessel using a hand-held mixing instrument and manuallyinserting the mixture into the medullary cavity with a suitableinstrument.

If a caulking gun or mechanical mixer is used, only a few seconds areneeded to effect satisfactory mixing. If manual mixing is used about twoto three minutes should be allowed for adequate mixing. In either eventthe gel time of the mixture should be sufficient to permit mixing andallow adequate time for the activities of the surgeon before theincision is closed.

The particular "B" components utilized in the invention most desirablycomprises a diamine, a short chain diol or triol and a relatively longchain glycol. The diamine, which is present in a relatively lowquantity, which depends on the reactivity of the "A" componentdiisocyanate, on the order of about 1% to about 50% by weight of the "B"component, is utilized to cause a rapid initial reaction with the part"A" prepolymer and thereby to allow the mixture to gel rapidly. Thisfeature allows the components of the invention to be inserted in a bonecavity, with the shank of the prosthesis inserted promptly thereafter.The rapid gel time allows the elastomer to "set up," holding the shankfirmly in place, allowing the surgeon to commence doing the incision atthat time, before the elastomer is fully cured. Particularly desirablediamines are 4 cyclohexane diamine, 4,4' methylene dianiline, 4,4'methylene bis (2.6 diisopropyl aniline), 1,8 diamino menthane, ethylatedtoluene diamines and polyoxy propylene diamines.

The diamine and/or relatively reactive diol or polyol is the primarycuring agent and is selected to provide higher physical properties byincreasing the crystalline hard segment concentration in the finalpolymer and a to create a maximum exotherm in the urethane-formingreaction. With an exotherm that does not exceed 150° and is preferablyabout 120° F., the incision can be closed when the urethane-formingreaction is not completed and the exotherm will not cause unacceptabletissue damage. Particularly desirable diols or triols for the curingagent are trimethylol propane, butane diol, 1,3 butylene glycol,diethylene glycol, triethyene glycol, tetraethylene glycol, and othersystems of similar equivalent weight.

A short chain glycol may be used as a "filler" or bulking agent, to makethe "B" component usable in reasonable volumes that make the "A" and "B"components easy to handle, so that 1 to 1 ratios by volume of "A" to "B"components are possible. The filler also participates in theurethaneforming reaction, so that all of the "B" components formchemical components of the final elastomer, making for a stronger, morecohesive elastomer from which components will not separate or leach out.A desirable range of filler equivalent weights is from about 300 toabout 2,000.

The relative portions of curing agent and filler in the "B" componentare respectively 5% to 50% and 25% to 95% by weight.

The following examples disclose preferred embodiments of the inventionand should not be interpreted as limiting the scope of the invention.

EXAMPLES Preparation of "A" Component Prepolymers

Prepolymer A was prepared using tolylene diisocyanate andpolytetramethylene ether glycol of molecular weight 1000 in a mole ratioof 1.7 to 1, such that a 4.2% isocyanate content remained after reactingfor 3 hours at 70° C.

Prepolymer B was prepared using tolylene diisocyanate and a polyethylenebutylene glycol adipate of 2000 molecular weight in a mole ratio of 2 to1 such that a 3.2% isocyanate content remained after reacting for 3hours at 70° C.

Prepolymer C was prepared using methylene bis diphenyldiisocyanate andapolytetramethylene ether glycol of 1000 molecular weight in a moleratio of 6 to 1 such that an isocyanate content of 16.8% remained afterreacting for 3 hours at 70° C.

Prepolymer D was prepared using methylene bis diphenyldiisocyanate and apolytetramethylene glycol of 2000 molecular weight in a mole ratio of 3to 1 such that an isocyanate content of 6.1% remained after reacting for3 hours at 70° C.

Prepolymer E was prepared using a combination of methylene bisdiphenyldiisocyanate and bitolylene disocyanate in a 9 to 1 ratio and apolytetramethylene ether glycol of 1000 molecular weight in a mole ratioof 3.2 to 1 such that an isocyanate content of 8.0% remained afterreacting for 3 hours at 70° C.

Preparation of "B" Components

Blend A of a polytetramethylene ether glycol of molecular weight 650 asa filler, and a relatively highly reactive curing agent of butane dioland methylene bis dipropylaniline was prepared in respective percentagesof 50%, 30% and 20% by weight, by heating all three blended ingredientsto 70° C., mixing them until homogeneous and allowing to cool.

Blend B of a 1000 molecular weight polydiethylene glycol ethylene glycoladipate as a filler, and a relatively highly reactive curing agent ofbutane diol and methylene bis dipropylaniline in respective percentagesof 50%, 30% and 20% by weight was prepared in the same manner as BlendA.

Blend C of a 650 molecular weight polytetramethylene ether glycol as afiller and a relatively highly reactive curing agent of butane diol andmethylene bis dipropylaniline in respective percentages of 75%, 20% and5% by weight was prepared in the same manner as Blend A.

Blend D was prepared using the same components as blend C in respectivepercentages of 60%, 30% and 10% by weight.

In each instance, equal quantities of the "A" components and "B"components described above were manually mixed for about two minutes inthe combinations shown in the following Table, under ambient conditionsat a theoretical stoichiometry of 100%. The results are listed in thefollowing Tables.

                  TABLE I                                                         ______________________________________                                               A       B                                                                     Com-    Com-    Mix   Work  Exo-  Shore                                Example                                                                              ponent  ponent  Life  Life  therm*                                                                              Durometer                            ______________________________________                                        1      A       A       1 Min  5 Min                                                                              140° F.                                                                      70A                                  2      B       B       2 Min 10 Min                                                                              140° F.                                                                      70A                                  3      C       C       1 Min 12 Min                                                                              150° F.                                                                      55D                                  4      D       D       4 Min 30 Min                                                                              105° F.                                                                      85A                                  5      E       D       5 Min 60 Min                                                                              102° F.                                                                      90A                                  ______________________________________                                         *By way of comparison, commercially available polymethylmethacrylate, suc     as that sold as "Surgical Simplex P Bone Cement," has an exotherm of          220° F.                                                           

                  TABLE II                                                        ______________________________________                                        Comparison of Physical Properties                                                      Tensile                                                                              Percent  Izod      Abrasion                                            Strength                                                                             Elonga-  Impact    (Mg.                                                (PSI)  tion     (Ft. Lbs.)                                                                              Lost)                                      ______________________________________                                        Polydimethyl-                                                                            1,000    500      9.0     Poor                                     siloxane                                                                      Polyethylenetere-                                                                        25,000    70      0.3     400                                      phthalate                                                                     Polyethylene                                                                             6,500    450      10.0    30                                       Polymethyl-                                                                              8,000     5       0.4     325                                      methacrylate                                                                  Example 1  1,800    400      No Break                                                                              12                                       Example 2  4,000    300      No Break                                                                              10                                       Example 3  3,200    275      No Break                                                                              1.7                                      Example 4  2,800    325      No Break                                                                              3.0                                      Example 5  3,000    300      No Break                                                                              2.5                                      ______________________________________                                    

The foregoing data demonstrate the improved wear properties availablewith the composition of this invention.

In the practice of the invention, when a patient is to have a prosthesisinserted, the surgeon will make an incision and ream out the end of thebone into which the shank of the prosthesis is to be inserted.

The excavation is than packed with a drying agent to remove blood andmoisture. A clotting agent is then applied to minimize blood flow.

The "A" and "B" components are then intimately mixed, as in a surgicallyusable caulking gun type of applicator, in a convenient volume ratiosuch as 1:1. This is preferably done with the evacuation of air from themedullary cavity, by the use of a vacuum pump, as the elastomer-formingmixture is extruded into the medullary cavity in the bone. The mixtureis of low viscosity as it leaves the caulking gun and flows easily intoand almost completely fills the medullary cavity but in about fiveminutes it has gelled sufficiently to have the consistency of soft, warmtable butter. This is sufficient to hold the prosthesis shank in place,so that the closing up procedure can begin. By the time that thesurgical opening is completely closed, say twenty minutes later, theelastomer has the consistency of hard cheese and is almost completelycured.

Thus, it will be seen that improved luting agents providing improvedphysical properties with a relatively low and more tissue-tolerableexotherm are available by practising the teachings of this invention. Itwill be appreciated that a great variety of "A" components and "B"components and combinations thereof are possible within the teachings ofthis invention. These variations may be utilized to minimize cost,control gel time, improve ease of handling, obtain improved physicalproperties and combinations of the foregoing. However, these variationsmay be made by a person having ordinary skill in the art, within thescope of and in accordance with the teachings of this invention.

It is also noteworthy that the invention may be used with prosthesismaterials other than stainless steel and ceramic, the particular "A" and"B" components being selected to provide good bonding to the prostheses,in addition to the other necessary physical and chemical properties.

Although the invention has been described in connection with prostheses,it it is also usable in connection with tissue-to-tissue bonding, as inmending broken bones.

Although the invention has been disclosed as comprising only aprepolymer, curing agent and filler, it is within the purview of thisinvention to incorporate additives in the reactants to modify theproperties of the end-product elastomer or regulate theelastomer-forming reaction.

I claim:
 1. A process for inserting a prosthesis into a medullary cavityin a human being or other animal comprising the steps of:(a) intimatelyadmixing a pharmaceutically acceptable poly(urea)urethane-formingprepolymer and a curing agent and filler; (b) promptly pouring thereactants set forth in step (a) into the medullary cavity; (c) insertinga prosthesis; and (d) completing the insertion of prosthesis, andclosing the incision made to permit the procedure, within a period inthe range from about five to about ten minutes after the reactants areadmixed.
 2. A process as set forth in claim 1, wherein the exothermcaused by the reaction when the ingredients are mixed in step (a) is notgreater than 150° F.
 3. A process as set forth in claim 2, wherein airis removed from the medullary cavity as the reactants are pouredtherein.